Graphical recording apparatus



June 16, 1959 MEZGER 2,890,921

GRAPHICAL RECORDING APPARATUS Filed A ril 15, 1954 EBIAS Fig. 3 Fig. 4

INVENTOR.

GEORGE ROBERT MEZGER AT TORNEYS United States Patent "ice 2,890,921 GRAPHICAL nnconnns o APPARATUS' George Robert Mezger, Teaneck, NJ., assignor to Allen B. Du Mont Laboratories, Inc., Clifton, NJ., a corporation of Delaware Application April 15, 1954, Serial No. 423,385

2 Claims. (Cl. 346-74) This invention relates to graphical electrical recording instruments.

An object is to provide a direct writing oscillograph, by which the recorded variation is immediately visible without the necessity of resorting to a long development process such as recording made on photographic film.

It is a further object to provide such an instrument with a linear, exponential or other non-linear response in accordance with certain mathematical functions or laws as desired.

Other objects of the invention will become apparent from a study of the specification and the drawing of which:

Fig. 1 is a diagrammatic illustration, in perspective, of the apparatus of the invention;

Fig. 2 is a graphical representation of measurement, according to the invention, of a sine wave, as it would appear on the recording paper;

Fig. 3 is a cross-sectional view taken on the line 3--3 of Fig. 1 of one specific embodiment of the invention, and

Fig. 4 is a cross-sectional view of another embodiment of the apparatus of Fig. 3.

With reference to Fig. 1, a roll of chemically treated paper 11, having the property of darkening when potential is applied between the surfaces thereof, passes from a supply roll 12 through a pair of rollers 13 and 14 onto a take-up reel 15. Any suitable motive power therefor may be provided, such as motor 36 attached to the takeup roller 15. The paper may be that currently available on the open market under the trade name of Alfax, manufactured by the Alden Products Corporation of Brockton, Massachusetts, or that available under the trade name of Faxpaper, manufactured and sold by the J. V. L. Hogan Corporation, of New York, New York The two rollers 13 and 14 between which the paper 11 passes may be said to be in roller juxtaposition, in that their axes are parallel and the surfaces joined in a line lightly making contact and permitting the passage of the paper 11 therebetween. One roller 13 has a surface of smooth metallic material which is electrically conductive. The other roller 14 is made of material having relatively high resistivity, such as carbon, and is made of uniform cross-section from end to end to produce a linear scale, or may be of a particular cross-section as explained hereinafter.

The high resistance roller 14 has a pair of slip rings 17 and 18 respectively on the ends thereof. A source 19 of signals to be measured is connected to the ends of the high resistance roller 14 through a pair of brushes 20 and 21 respectively making contact with the slip rings 17 and 18.

The conductive roller 13 is connected to one terminal of the source 19 of signals which preferably is the grounded terminal so that the conductive roller 13 operates at ground potential. With this arrangement a potential ditfereuce exists between the surface of the v Patented June 16, 195 9 vresistance roller 14 and the groundedconductive roller 13. The extent of existence of this potential between the surfaces of the two rollers 13 and 14 along the longitudinal length thereof is dependent upon the amount of resistance of the high resistivity roller 14.

The special or chemically treated paper 11 in passing between the rollers 13 and 14 is darkened along one edge thereof, i.e., adjacent the high potential slip ring as at 17, and laterally across the paper a distance dependent upon the resistance of the material of the high resistance roller 14 and the potential applied to the slip ring 18 through the brush 21 from the source 19 of signals. Thus with a given roller having a given resistance the extent of darkening laterally of the paper 11 is directly dependent upon the value of the potential applied to the slip ring 18 at one edge thereof, or the potential applied between the slip rings 17 and 18.

In order that a reference base may be established a source 30 of bias voltage is connected between the source 19 of signals and one brush 20 connected to a slip ring 17 on one end of the resistance roller 14. This bias voltage preferably is constant so as to establish a reference line or edge of darkened area on the paper, the darkened area extending laterally from one edge of the paper and the edge extending longitudinally as a result of the passing of the paper between the rollers 13 and 14. The graphical representation of the darkened area of the paper established by the bias voltage is illustrated in Fig. 2 existing between the dotted lines 31 and 32.

A signal from the source 19 applied between the brushes 20 and 21 will vary the amount of darkened area by varying the lateral extension thereof across the paper 11. The elfect of a sine wave from the source 19 is illustrated in Fig. 2. The sine wave is applied to the brushes at a time indicated at T on the dotted line 32 and the graphical representation of the sine wave is illustrated between the dotted lines 32 and 33. Any varying signal from the source 19 will affect the paper by darkening the area in like manner and the edge of the darkened area will show the type of signal being measured and the variations involved therein.

A linear scale of measurement may be produced by providing a high resistance roller 14 of uniform crosssectional area. A non-linear scale may be produced by providing a particularly shaped axial core 22 of insulating material within the carbon roller 14 as shown in Figs. 3 and 4. In Fig. 3 the core 22 of insulating material is a conical section with exponentially curved sides as shown. This arrangement will produce an exponential scale. In Fig. 4 the core 22 is shown as comprising an insulating section having a reduced cross-sectional dimension along a portion thereof. This structure will result in expansion of details of the signal between two selected limits created by the core area between the lines 34 and 35.

Further modifications are possible by employing a dielectric type paper or covering the roller 13 with a dielectric material, thus permitting the paper 11 to be charged to varying degrees.

While specific embodiments have been illustrated and described, it is apparent that modifications are possible without departing from the teaching of the invention defined by the following claims.

What is claimed is:

l. Graphical recording apparatus comprising a sheet of material having the property of darkening when an electrical potential is applied between the surfaces thereof, a pair of rollers in roller juxtaposition, said rollers comprising a first roller of electrically resistive material having a first slip ring on the one end thereof, and a second slip ring on the other end, a second roller of 3 I 4 conductive material of relatively low resistivity, means potential is connected between said first slip ring and maintaining said second roller at ground potential, means ground.

for connecting a varying electrical potential to be recorded between said sllp rings, means for malntainlng eferences Cited In the file of thls Patent said first slip ringat ground, whereby a potential gradient 5 UNITED STATES PATENTS is established along the length of said first roller rela-' 2,384,722 Blain Sept. 11, 1945 five 10 said second roller and means for passing said 2,391,768 Blain Dec. 25, 1945 material between said rollers. 2,527,599 Terry Oct. 31, 1950 2. The device of claim 1 in which a direct current bias 2,704,700 Hahn Mar. 22, 1955 

